There are three conditions for a sin to be mortal:

  1. It must be a grave sin. Eg. Anything from the 10 commandments, Adultery, Murder etc.
  2. It must be committed with full consent of the will.
  3. The person who commits the sin must be aware that it is a grave sin. ("Full knowledge")

This leads me to wonder, are non-Catholics who don't believe in mortal sin by that very fact, immune from committing mortal sins? My reasoning is that, a person who doesn't believe in mortal sin could be said to be "unaware" that their sins are grave, and if they are "unaware" that their sins are grave, then their sins are not mortal, therefore they won't go to Hell (I think the correct terminology is to say that they are in invincible ignorance).

Extrapolating this line of reasoning, doesn't this mean that most if not all non-Catholics will be saved? Because these non-Catholics are presumably "unaware" that they have to be part of the Catholic church in order to be saved. And if they are "unaware" of this then they are not in a state of mortal sin because they don't have full knowledge and are thus in invincible ignorance and wont go to Hell.

On the other hand, imagine that the non-Catholic has only met a single Catholic in their entire life and the only thing that the Catholic said to them was "you have to convert to my religion or you will go to Hell". In this case is the non-Catholic still "unaware" that they need to join the church or does a brief warning such as this count as being given "Full knowledge"?

Finally, it seems possible to say that all non-Catholics are in a state of invincible ignorance, because if they had full knowledge that they have to become Catholic to be saved, then they would hurry up and convert. But they don't do this, so it seems fair to assume that they are unconvinced and therefore unaware. (Who on earth would become sincerely convinced that to go to Heaven and avoid Hell they have to join the Church, and then not do it?)

In summary my questions are

  1. How is it possible for a non-Catholic to commit a mortal sin? and
  2. Are all non-Catholics in the state of invincible ignorance as per my reasoning above, and if not, where did I go wrong?
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    If newly converted , yet previously baptized individuals must go to confession in order to be members of the Catholic Church, it stands to reason that they could be capable of seriously sinning against God. Nevertheless I feel you are asking to much in a single question. In the end you are asking two separate questions that I feel should be addressed on their own merit.
    – Ken Graham
    Commented Jan 31, 2017 at 4:46
  • Agreed - split these into two questions and we'll tackle each separately. Commented Jan 31, 2017 at 14:03
  • Are you looking for a Catholic answer (are those not part of the church subject to what they believe is a mortal sin) or a non-Catholic answer (is a mortal sin something that they believe they are subject to)? Right now, you have one of each in response to this question. Commented Feb 1, 2017 at 6:45
  • 1
    @Thunderforge I'm looking for a catholic answerq Commented Feb 1, 2017 at 7:22

1 Answer 1


If the non-Catholic is not baptized, the non-Catholic has original sin and is damned, "unless before the end of life the same have been added to the flock," as Pope Eugene IV puts it in his Cantate Domino.

If the non-Catholic is baptized, he does not have original sin, but he can certainly commit actual sins (mortal or venial).

Cain and Onan—who committed the sins of fratricide and contraception, respectively—were before Christ, yet that did not except them from sin.

  • 1
    How is it possible for non-Catholic to commit a mortal sin, given the reasoning in the question? Commented Jan 31, 2017 at 2:46
  • 1
    I've seen it reasoned that Onan's sin was not contraception, it was violating the law about taking the wife of his brother per the law. Commented Jan 31, 2017 at 2:54
  • @TheIronKnuckle Sin is the baseline condition of all of mankind since the Fall. See the doctrine of Original sin. That's how, and that's the perspective that this answer is coming from. Commented Jan 31, 2017 at 2:56
  • @KorvinStarmast I'm zeroing in on this answer's second paragraph when I ask "How?". Assuming that they are baptised, how is it possible for them to commit mortal sins if they are unaware that it is even possible to commit mortal sins? Commented Jan 31, 2017 at 2:59
  • 2
    I don't see why Protestants would be unable to distinguish grave sin from venial sin. For example, could they commit adultery without knowing it is a grave sin?
    – zippy2006
    Commented Jan 31, 2017 at 20:30

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